A vehicle air bag system is typically manufactured as a module and thereafter installed in a vehicle. A standard air bag module includes a folded air bag, an inflator or gas generator for inflating the air bag, and a container which encloses the air bag. Upon actuation of the inflator, gas at relatively high pressure is directed into the air bag, thereby deploying it through a portion of the container and inflating it to a predetermined configuration. The container is usually comprised of a reaction device and a cover. During deployment of the air bag, reaction forces are absorbed by the reaction device.
On the driver side of vehicle, the air bag module is commonly incorporated into the steering wheel. For example, in FIG. 1 of U.S. Pat. No. 4,828,286 to Fohl, an air bag module is disclosed which includes an air bag, an inflator, and a container comprising a reaction plate and a cover. The module is preassembled as a unit and is thereafter attached to the vehicle steering wheel by bolting the reaction plate to a structural member of the wheel.
Because space requirements are increasingly important in vehicle design, it is important that an air bag system be constructed from a minimum number of components and be as compact as possible. Also, as the number of air bags being installed in vehicles increases, it becomes increasingly important to provide efficient and effective ways of mass producing these air bag systems.
In the past, suggestions have been made for air bag systems which reduce both the number of parts and the total number of procedures required to construct the system. For example, U.S. Pat. No. 4,877,264 discloses an air bag module and method of assembly wherein a single retaining ring is used to secure an air bag and an inflator to a mounting plate. The inflator is first centered on the mounting plate. Thereafter, an assembly comprising an air bag and a retaining ring is lowered over the inflator. The assembly is attached to the mounting plate by lockingly engaging the retaining ring to the mounting plate. In attaching the retaining ring to the mounting plate, both the air bag and the inflator are secured to the mounting plate without requiring any additional fasteners.
While the air bag module of U.S. Pat. No. 4,877,264 eliminates some of the components of a conventional air bag module, it still includes a separate mounting plate to which the remaining components of the module are attached. It also includes a separate air bag retaining device intermediate the inflator and the mounting plate. Each of these items adds size and weight to the air bag module. Moreover, the presence of these items increases the complexity of the module and, accordingly, the number of procedures required to assemble the module.